Traditional paper manufacture begins with the processing of its primary raw material, which is cellulose fiber. Most woods are made up of roughly 50% cellulose, 30% lignin and 20% of mixtures of aromatic hydrocarbons and hemicellulose carbohydrates. In order to obtain cellulose in usable form for paper manufacture the wood is normally pulped to separate the fibers and remove the impurities. The higher the cellulose content of the resulting pulp and the longer the fibers, the better the quality of the paper. Hardwoods generally contain a higher proportion of cellulose but of shorter fiber length than softwoods, which are more resinous. Lignin acts as the resinous adhesive that holds the fibers together. Cotton, linen, straw, bamboo, certain grasses and hemp are also sometimes used as a source of fiber for papermaking. The pulp used in papermaking is the result of the mechanical or chemical breakdown of fibrous cellulose materials into fibers which, when mixed with water, can be spread as thin layers of matted strands. When the water is removed the layer of fibers remaining is essentially paper. Various materials and chemicals are often added to give the paper a better surface for printing, greater density or extra strength. These materials and chemicals are not always cost effective or environmentally friendly.
In addition to cost and environmental considerations, improvements in paper design, production and quality are currently the paper manufacture industry's highest priorities. Pulping, process chemistry, paper coating and recycling are key areas that can benefit from the nanotechnology field, such as polyelectrolyte layer-by-layer (L-b-L) self-assembly. An environmentally friendly process offered by L-b-L nanoassembly may provide important development to the industry.
In the last decade electrostatic layer-by-layer (L-b-L) self-assembly techniques have been developed as a practical and versatile way of creating thin polymeric films both on large surfaces and on microcores. These techniques allow the design of ultra thin coatings with a precision better than one nanometer, and with defined molecular composition. The method of this invention incorporates the use of these layer-by-layer self-assembly techniques as a step in a plurality of sequential unit operations designed to manufacture paper of improved strength and enhanced surface properties. It is an object of this invention to provide a method for the manufacture of paper of improved strength and enhanced surface properties. It is also an object of this invention to provide a cost-effective process for fabricating paper using nanotechnology layer-by layer self-assembly techniques. Another object of this invention is to provide an application of nanotechnology layer-by-layer self-assembly techniques to paper manufacture that is particularly suitable to the treatment of wood fibers and lignocellulose pulps containing broken (mill broke) recycled fibers so as to allow the cost-effective use of such pulps in the manufacture of paper with enhanced strength and surface properties. These and other objects of the invention will become apparent from the reading of the description that follows.